AeroRocketCAD Conversion program
AeroRocketCAD for Airframe & Nozzle Shapes
AeroRocketCAD
Convert AutoCAD DXF Drawing Files
to AeroRocket Import-Shape Formats
GO ...
&
 
AeroGRID
Generate Fluid Boundary Shapes
for AeroCFD, AeroWindTunnel and Nozzle
GO ...

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Copyright 1999-2015 John Cipolla/AeroRocket. All rights reserved
 

AeroRocketCAD converts AutoCAD DXF drawing file LINE and ARC entities to import-shape file formats for AeroCFD, Nozzle and AeroWindTunnel. This program is provided FREE of charge for purchasers of all AeroRocket fluid dynamics programs that utilize 2-D and 3-D import-shape geometry. Also, quickly generate fluid boundary surfaces using the new AeroGRID design utility by generating TOP and SIDE views of realistic 3-D airframes for AeroWindTunnel or complex 3-D axisymmetric and 2-D shapes for AeroCFD and Nozzle.

AeroRocketCAD (TOP)

Figure-1, DXF conversion as it appears after clicking, Open DXF Geometry using Zoom then using X-TRANSLATION and Y-TRANSLATION

DXF FILE CONVERSION (SEE FIGURE-1 AND FIGURE-2
1) To Open and convert an AutoCAD .DXF drawing file, click File then click Open DXF Geometry. Please see Figure-1.
2) Find and click a .DXF drawing file previously created by AutoCAD. AutoCAD generated LINES and ARCS will appear in the lower left of the plot area.
3) Use ZOOM to enlarge the drawing and to make all segment numbers visible. If required use X-TRANSLATION and Y-TRANSLATION to make all segment numbers visible. Please see Figure-1.
4) In Highlight segments insert segment numbers that represent the fluid boundary. Use Highlight segments to note the location of all drawing file LINE and ARC entities that appear in the converted AutoCAD DXF drawing file. Please see Figure-1.
5) In the Vertical Text Box, enter LINE and ARC segment numbers that define the fluid boundary. The numbering sequence must be from left to right. However, it should not matter in what sequence the curves were generated in AutoCAD. Use CLEAR to start over. Simply backspacing will confuse the program and unpredictable shapes will occur. CLEAR must be used to start over. Remember, insert each segment number and then click Enter. Please see Figure-1.
6) To generate a AeroCFD, Nozzle etc. fluid boundary click the Generate fluid boundary in converted coordinates option button. No fluid boundary will be generated until the segment numbers are input using the procedure outlined in item 5. Please see Figure-2.
7) Click File then Save XXX Geometry As ... to save the converted shape as an import file for use with AeroCFD, Nozzle, etc. Please see Figure-2.

8)
When initially importing a new shape into AeroCFD, click File then Import Shape to input a geometry file created in AeroRocketCAD. Then, in AeroCFD define the flow and mesh parameters and save the project file by clicking File then Save Project As. Subsequently, to run a project and its associated airframe shape the shape file is imported first and then the project file is opened. Running a previously saved shape-project is performed by first clicking File then Import Shape and finally by clicking Open Project. Please wait for the shape and mesh parameters to be generated before performing each step. The data has the following format. First line: Total number of X-Y point locations, maximum of 1000 points. Second and subsequent lines: X, Y airframe locations separated by commas. A AeroCFD shape file defines the upper contour of an axisymmetric airframe geometry starting from nose-tip to the end of the airframe.

9) Please see the AeroCFD analysis that generates the geometry of a Coke Bottle using DXF formatted data.


OPTIONAL INPUT DATA
9) Identify each .DXF drawing file segment by inserting individual segment (curve) numbers into the Highlight segments data entry box.
10) In the Number of grid points per segment data entry box increase or decrease the number of grid points on each fluid boundary segment by inserting a new number of grid points.
11) Make the generated surface an Internal flow boundary for Nozzle by checking the bottom most check box. If the check box is unchecked the surface is an External boundary (AeroCFD, AeroEuler) and if the check box is checked the surface is an Internal boundary (Nozzle).


Figure-2, DXF conversion as it appears after entering segment numbers 6,2,3,4,5 then clicking the Generate fluid boundary in converted coordinates option button
 

AeroGRID (TOP)

AeroGRID is a stand-alone computer program accessed from within AeroRocketCAD used to generate fluid boundary shapes by specifying the TOP View and SIDE View for AeroWindTunnel or complex axisymmetric and two-dimensional fluid boundary shapes for AeroCFD and Nozzle.


Figure-3, AeroGRID generated shape using four grid points and Cubic Spline smoothing. This shape was successfully run in AeroCFD at Mach 2

AEROGRID FLUID BOUNDARY GENERATION
1) To generate a fluid boundary for AeroCFD, AeroWindTunnel or Nozzle without a DXF drawing file, in the top pull down menu click Number of Grid Points then select the number of grid points required to define a fluid boundary. 2 to 20 grid points may be selected using the pull down menu. Please see Figure-3.
2) In Total Length (X) specify the total length of the fluid boundary. This length represents total airframe length for AeroCFD and AeroWindTunnel or total nozzle length for the Nozzle program.
3) Using the Point number option buttons and the Y-COORDINATES slider bar define a fluid boundary shape for the number of grid points selected.
4) After the shape is specified use the Generate fluid boundary using interior points option button to plot the resulting fluid boundary grid points.
5) Change the number of grid points on each segment of the fluid boundary by inserting a new value in the Number of interior grid points per segment data entry box from the default value of 20 to any number ranging from 2 to 1000. Remember, the total number of grid points on the fluid boundary is limited to 1000 because of program (AeroCFD, Nozzle, etc) limitations.
6) Click File then Save XXX Geometry As ... to save the fluid boundary shape as an import file for AeroCFD, Nozzle, etc. Please see Figure-3.
7) Click the SMOOTH CURVE command button to smooth the fluid boundary using a Cubic Spline curve fit of the available grid points. See Figure-4.


AEROWINDTUNNEL AIRFRAME GENERATION
8) Repeat STEP-1 and STEP-2 as before. Then, use the Point number option buttons and the Y-COORDINATES slider bar to define the TOP View for imported airframes. Then, in the bottom section click the Generate airframe PLAN view (top) option button when one half of the TOP View is specified. SMOOTH curve if required. The TOP view is now specified.
9) Then, using the Point number option buttons and the Y-COORDINATES slider bar define the UPPER part of the airframe SIDE View. Then, click the Generate airframe UPPER side view (+height) option button when the upper half of the airframe SIDE View is specified. SMOOTH curve if required. The upper half of the side view is now specified.
10) Then, using the Point number option buttons and the Y-COORDINATES slider bar define the LOWER part of the airframe SIDE View. Then, click the Generate airframe LOWER side view (-height) option button when the lower half of the airframe SIDE View is specified. SMOOTH curve if required. The lower half of the side view is now specified.
11) Finally, to save the AeroWindTunnel airframe geometry first click File then, Save AeroWindTunnel Geometry As ... Please see Figure-3.
Please note every time the Point number option buttons and the Y-COORDINATES slider bar are modified a new TOP/SIDE View may be specified.


Figure-4, AeroGRID generated shape using three grid points and Cubic Spline smoothing for generating AeroWindTunnel TOP View


Figure-5, AeroGRID generated shape using three grid points and Cubic Spline smoothing for generating AeroWindTunnel UPPER side View


Figure-6, AeroGRID generated shape using three grid points and Cubic Spline smoothing for generating AeroWindTunnel LOWER side View


Figure-7, AeroWindTunnel screen after importing AeroGRID shape file
 

NOZZLE FLUID BOUNDARY GENERATION
1) To generate a fluid boundary for Nozzle without a DXF drawing file, in the top pull down menu click Number of Grid Points then select the number of grid points required to define a fluid boundary. 2 to 20 grid points may be selected using the pull down menu. Please see Figure-8.
2) In Total Length (X) specify the total length of the nozzle fluid boundary. This length represents total nozzle length.
3) Using the Point number option buttons and the Y-COORDINATES slider bar define a fluid boundary shape for the number of grid points selected.
4) After the shape is specified use the Generate fluid boundary using interior points option button to plot the resulting fluid boundary grid points.
5) Change the number of grid points on each segment of the fluid boundary by inserting a new value in the Number of interior grid points per segment data entry box from the default value of 20 to any number ranging from 2 to 1000. Remember, the total number of grid points on the fluid boundary is limited to 1000 because of program Nozzle limitations.
6) Click File then Save XXX Geometry As ... to save the fluid boundary shape as an import file for Nozzle.
7) Click the SMOOTH CURVE command button (optional) to smooth the fluid boundary using a Cubic Spline curve fit of the available grid points.


Figure-8, AeroGRID shape using four grid points for generating Nozzle boundary shape


Figure-9, Nozzle screen after importing AeroGRID boundary shape file

Cubic Spline smoothing
Figure-10, AeroGRID uses Cubic Spline smoothing to connect non-smooth fluid boundary segments

The Cubic Spline used in AeroGRID is a method to draw a smooth curve through specified end-points as if using a French curve or a draftsman's spline. Smoothing coefficients allow the combined fitting function F(x) to be a combination of smoothly joined cubic segments, f(x). If the combined fitting curve is called F(x), then F(x) is represented by n segments [fi(x), i = 0, n - 1] each of which can be written as fi(x) = a0i + a1i(x-xi) + a2i(x-xi)2 + a3i(x-xi)for xi < x < xi+1 and i = 0, n - 1. Save AeroGRID's Cubic Spine smoothing coefficients by clicking File then Save Smoothing Coefficients As ... Please see Figure-3 and Figure-4.

REFERENCES
AutoCAD 2009 DXF Reference manual by Autodesk


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